1. Field of the Invention
This invention relates to a recording apparatus, a recording and/or reproducing apparatus and a recording method for digital signals in which digital signals are recorded on plural slanted tracks of a tape-shaped recording medium.
2. Description of the Related Art
In a system for recording digital signals to a high density on the tape-shaped recording medium, such as a digital audio tape recorder (DAT), a head 100 is adapted to scan a magnetic tape 101 as a tape-shaped recording medium in an oblique direction A2 relative to the running direction A1 for recording/reproduction, as shown in FIG. 1.
Therefore, in such system, plural slanted tracks are formed for extending obliquely relative to the running direction A1 of the magnetic tape 101. In a so-called azimuth-beta recording system in which no guard band is provided, a track width t2 on the magnetic tape 101 is narrower than a head width t1. That is, during recording, a posteriorly recorded slanted track is overlapped with a portion of a neighboring previously recorded slanted track.
With such system, first-time recording can be done unobjectionably. However, if new digital signals are overwritten on previously recorded digital signals, for junction recording or after-recording, a newly recorded slanted track 102a is partially overlapped with a previously recorded slanted track 102b thus erasing a portion of the previously recorded slanted track 102b.
Specifically, if, after recording is performed in an editing operation with tracking control, the previously recorded slanted track is erased by approximately 0.25 track pitch by the overwriting slanted track during punch-in operation, while the previously recorded slanted track is erased by approximately 0.5 track pitch by the overwriting slanted track during the punch-out operation. If the previously recorded slanted track is erased by as much as 0.5 track pitch, there is produced an error that cannot be corrected during reproduction.
Thus, in a system employing a rotary head for recording digital signals to a high density on the tape-shaped recording medium, there is presented a problem that a previously recorded slanted track is partially erased at the time of junction recording or after-recording.
This problem is thought to be inherent in the azimuth beta recording system in which the track width is narrower than the head width. Owing to this problem, there is placed a limitation to using the DAT, which is an inexpensive medium for household use, in an professional application entailing high signal quality.
Meanwhile, in a system typified by DAT, input digital signals are divided into even-numbered data and odd-numbered data and interleaved and the interleaved data are distributed in plural slanted tracks for recording, for thereby copping with burst errors ascribable to dropout in the magnetic tape as the tape-shaped recording medium. However, such interleaving has no effect if the error rate of some slanted tracks in their entirety is worsened to render it difficult to obtain the playback output.
As a system for coping with this problem, there is proposed in a senior Japanese Laid-Open Patent No.08102150 a DAT of the present Assignee wherein data is divided into upper order bits and lower order bits and in which the lower order bits are recorded on the slanted track susceptible to dropout by junction recording or after-recording. With such DAT, if signals of some slanted tracks are lost by dropout under the effect of the junction recording or after-recording, the upper bits are reproduced normally, thus realizing a satisfactory playback output.
However, if this DAT is applied as a DAT carrying out recording and/or reproduction at double the usual recording and/or reproducing speed (double-speed DAT), it is upper 16 bits of the input digital signal that are handled as upper bits. Therefore, if the original audio data is 24-bit data, and if part of the slanted track is erased due to junction recording or after-recording, the lower 8 bits of the audio data are lost by dropout. Thus, even the DAT proposed in the above referenced patent application is insufficient for recording digital signals exceeding 16 bits.
If only lower order bits are recorded in specified slanted tracks, it may occur that, in reproducing the magnetic tape with a relative movement speed between the magnetic tape and the head different from the usual playback speed, that is in reproducing the tape with variable playback speed, the playback sound cannot be produced. For example, if, during variable speed reproduction, tape running control should fail to operate normally and the head moving position on the magnetic tape deviates from the design position, such that the playback signal is produced from the slanted track on which only the lower bits are recorded, the playback sound cannot be produced due to lack of the upper bits in the slanted track. That is, the DAT proposed in the senior patent application presents problems especially in connection with variable speed reproduction.